THE PRESENT INVENTION relates to a seat for use in a vehicle and more particularly relates to a seat intended for use in a passenger transport vehicle such as a car, lorry or bus.
The present invention seeks to provide a seat suitable for damping the effects of a high pressure impact against the seat back-rest by the occupant of the seat, as may occur, for example, in the event of a rear impact. Such high pressure impacts often cause injuries termed "whiplash" injuries.
A conventional vehicle seat consists of a seat squab and a back-rest. The squab and the back-rest may be cushioned and upholstered. Typically, the lower part of the back-rest is attached to the rear part of the seat squab. It is common for a recliner mechanism to be provided which forms the connection between the lower part of the back-rest and the seat squab which enables the angle of inclination of the back-rest to be altered. The recliner mechanism thus comprises an adjustment mechanism. It is also conventional for a seat to be mounted to be moved forwardly and rearwardly, for example to permit the position of the seat to be adjusted to suit the length of the legs of the occupant. In some vehicles, part of the vehicle seat back-rest can be moved in relation to the lower back of the occupant to provide adjustable lumbar support.
If a first vehicle, which is stationary or moving only at a low speed, is hit from behind by another vehicle which is travelling at a greater speed, initially the chassis of the first vehicle is accelerated forwardly. Because the chassis is accelerated forwardly, each seat in the vehicle, which is connected to the chassis, is also accelerated forwardly. Because of the inertia of an occupant of the seat, the lower torso of the occupant will be pushed against the lower part of the back-rest of the seat as the seat accelerates. Since the upper part of the torso is typically not in contact with the back of the seat, the upper part of the torso cannot readily follow this movement.
Consequently, the lower part of the torso of the occupant executes an apparent forward motion, while the head of the occupant stays virtually stationary for a brief moment. This movement eventually results in a severe rearward bending of the neck, and may cause ligaments, and other soft tissue in the upper neck, to tear.
Subsequently, in a rapid movement, the head is typically thrown forwardly in a rebound and may be pressed forcefully against the chest of the occupant. This may tend to amplify injury caused during the first movement.
The movement described above can occur with prior proposed seat designs, since when an occupant is sitting on a vehicle seat, there is, typically, a gap between the neck or head of the occupant and any head-rest or head restraint mounted on the seat.
It has been proposed to provide seats in motor vehicles which are designed to minimise the risk of injury to the occupant of the seat in the event that a rear impact should occur.
EP-A-0,556,884 discloses a seat assembly which has a seat squab and a back-rest, the back-rest being adapted to move rearwardly relative to the seat squab when subjected to a severe loading by the occupant of the seat during a rear collision. The back-rest of the seat has side supports which are pivotally connected to slide members, the slide members being adapted to move with a horizontal linear movement in horizontally extending channel members secured to the squab of the seat. An energy-absorber is provided to absorb energy as the side members move rearwardly relative to the seat.
In the event that a rear impact occurs, the occupant of the seat moves rearwardly and imposes a rearward force against the back-rest of the seat. The seat-back moves rearwardly with the slide members sliding relative to the channels. During this movement, energy is absorbed by the energy absorber.
The seat-back can also, at the same time, pivot rearwardly until further rearward movement of the seat-back is prevented by a wire which has one end secured to the seat-back and the other end secured to a floor panel of the vehicle.
Since the back of the seat can pivot rearwardly, there is no mechanism that brings the head-rest that may be mounted on the seat swiftly to a position adjacent, or into contact with, the head of the occupant of the seat. Consequently, this particular seat design does not remove the risk of whiplash injury occurring.
U.S. Pat. No. 3,802,737 also discloses a safety seat intended to protect the occupant of a vehicle during a rear impact. Instead of being rigidly mounted in position, the squab of the seat is connected to the floor of the vehicle by means of a pair of link arms, and the head-rest of the vehicle seat is connected to the back of the seat by means of an adjustable linkage.
In the event that a rear impact occurs, the squab of the seat, together with the back of the seat, are both tilted forwardly about the link arms connecting the seat to the floor of the vehicle, and as a consequence of pressure being applied to part of the linkage supporting the head-rest by rearward movement of the torso of the occupant of the seat, the head-rest is brought into contact with the rear of the head of the occupant of the seat. The described arrangement does have exposed linkages which may tend to jam.
The present invention seeks to provide an improved seat for use in a motor vehicle.